This invention relates to a method for preparing a supported hydroconversion catalyst, particularly with respect to improved hydrodenitrification (HDN) activity.
Considerable research has been undertaken to develop and commercialize new, cost effective highly active hydroconversion catalysts for large volume first stage hydrocracking and catalytic cracking feed hydrotreater applications. The inclusion of significant amounts of 1000.degree. F..sup.+ residual components, including cracked stocks, in the hydrocarbon feed to these processes has created severe activity and stability problems for the catalysts currently used commercially in these applications. The growing demand for new catalysts for up-grading such poor quality feedstocks has led to the discovery of an improved catalyst by a special technique for adding additional catalytically active metals onto supported catalysts.
Methods for preparing supported hydrogenation metal catalysts which are suitable starting points for the instant invention are well known. For example, Adams, U.S. Pat. No. 3,629,146, which is incorporated herein by reference, relates to a method for preparing a supported catalyst containing high catalytic metal concentrations in a single aqueous impregnation from a stabilized solution. It is also known to combine molybdenum carbonyls with alumina to prepare a catalyst for the metathesis of olefins J. Mol. Catalysis, 1 (1975/76)77-84. Surprisingly, I have discovered that the hydrodenitrification activity of commercial hydrotreating catalysts can be greatly improved by adding small amounts of molybdenum and/or tungsten carbonyls to said catalysts by sublimation.